P38A To MAF or not to MAF, that is the question.....

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Curiouser - Replaced the MAF with a new one - and runs worse, won't idle without some input to the pedal, won't pull away, then dies even with foot on throttle....

Unplug it and she idles well, pulls away well, but doesn't like being under load i.e. a slight gradient etc.

Also, got a P0102 Code with the replacement MAF too....

I am wondering if it could be O2 sensors also.....the 1178 and 1176 codes have not returned.
 
Saint.V8 said:
Research is leading me to air leaks for P1176 and P1178....the fuelling has reached the end of its designed limit - and she does smell very rich when running.
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Gorsky's 4.6 has been standing all summer. Tried running last weekend and it was all over the place. Ran rough as f*ck. Stalled while idling on LPG but ran OK with the revs up. Running on petrol was rough as hell but it idled, although sounding like it missed a beat once in a while. My conclusion is that these cars don't like not being used!
 
Grrrrrr said:
Gorsky's 4.6 has been standing all summer. Tried running last weekend and it was all over the place. Ran rough as f*ck. Stalled while idling on LPG but ran OK with the revs up. Running on petrol was rough as hell but it idled, although sounding like it missed a beat once in a while. My conclusion is that these cars don't like not being used!
Click to expand...
They never go wrong if never used.:rolleyes::D:D
 
I'd try to borrow a nano or try to check if the lambdas are changing ie is it running closed loop.
Try the tps check it's values unplug it when it's running. Was the maf definitely good? Does your maf work on another vehicle. Unplug the cam sensor try and start. The maf doesn't really work until after 550revs. So the tps and the maf work together and corelate values.
It seems like it's over fueling only on bank 2?
 
Reet......update.....

Recap: New MAF fitted, car was worse than ever - hated it so took it back. After research, the GEMS should die after 550rpm if MAF faulty as there is no default strategy emplyed when MAF goes south (apparently).

Have completed the following tests and here is 'Drivability Matrix' of how she performs:

P38_Drivability.jpg


I am thinking it is O2 sensors affecting fueling mixture - but both of them going south at the same time - chances??

A security guard at the gate I passed on my way to do a fast run says it smelt running lean, not rich - which is odd as with the O2 sensors unplugged it should run a rich fuel map!!

Plugs out later to have a look if they have any colour to them - but they are only a few days old and not done more than 15 miles yet!

Thoughts are indeed welcome as I am running out of ideas and there is a possibility I can't see the wood for the trees.....
 
Saint.V8 said:
Reet......update.....

Recap: New MAF fitted, car was worse than ever - hated it so took it back. After research, the GEMS should die after 550rpm if MAF faulty as there is no default strategy emplyed when MAF goes south (apparently).

Have completed the following tests and here is 'Drivability Matrix' of how she performs:

View attachment 160548

I am thinking it is O2 sensors affecting fueling mixture - but both of them going south at the same time - chances??

A security guard at the gate I passed on my way to do a fast run says it smelt running lean, not rich - which is odd as with the O2 sensors unplugged it should run a rich fuel map!!

Plugs out later to have a look if they have any colour to them - but they are only a few days old and not done more than 15 miles yet!

Thoughts are indeed welcome as I am running out of ideas and there is a possibility I can't see the wood for the trees.....
Click to expand...

Fit an M51. ;):D
 
Further confusion.....

With the O2's disconnected, the system is supposed to go into an open state and use a base fuel map which runs rich to protect the engine apparently.

I have the MAF disconnected and the O2's disconnected, but when I plugged it into diagnostics, it said it was in a closed state using Oxygen Sensors for Normal Operation, the O2 sensor voltages should 0.210 or 0.205, and the Short Term Fuel Trims where going from 0% to -25% (Lean) with the long term trims reading +24.22% (Rich).....

When the STFT went down to 0% it ran well and accelerated like a train, but then they would creep back up over about 5-7 seconds to -25% and she'd run like a dog......if you then revved it up, the STFT would then switch to 0% and she'd be good, then a few moments later she'd creep back up to -25% STFT and run like a dog.

I think I need to clear the LTFT and see what happens.....but I don't have a device capable of doing so.

Also, why would the system think all is well, with no fault codes and still run closed loop with the MAF and O2's disconnected.????
 
It may be your diagnostics aren't working with the gems system. I'll relate my take of work( quickly)
A week after a hose popped off (after a major rebuild) I was left stranded about 10 miles away. It wouldn't start and after much messing and unplugging it would start with clouds of smoke .
After weeks and months of messing and getting very frustrated even learning to read the wiring diagrams and checking continuity from ecu to sensors. Then changing the entire engine loom .
It was none of them. After some emails to mark adams and reading a random post about the same I had a look in the ecu.....bingo a burned track it. I still didn't know the cause though. I could repair the track with a jumper once then it blew something more than a track. Anyway eventually I discovered that the maf and the cam sensor have the capability of blowing tracks in the ecu if a. The wires are frayed around the cam/ mad or b. A Mickey mouse aftermarket maf has been used.
Check out these things as different tracks blow causing different symptoms. It took me many months to reach this conclusion.
PS when it was fixed with a new ecu and a new sensor it just worked!
Mark adams (tornado chips) is a lovely bloke and suggests it's much more common and certainly something worth checking.
I amazed some guys by diagnosing a similar fault on this forum(it was different ecu track) unfortunately the guy wasn't very technical and just stopped posting(scrapped)
Just check because your vehicle sounds like it's not responding like it should to the changes you've made.
 
What had happened was the coolant hose popped soaking the cam sensor in hot coolant. This gradually shorted. Then Everytime I put a new ecu in the instant the key turned the track blew. Finally unplugged all the sensor I could and swapped the ecu. Much better.
 
PS look carefully at the ecu I looked once and didn't see it. Second time I spotted it!
What I think made it truly difficult was I had to unplug the cam sensor then change the ecu ( doing the security thing) before it started working in any sensible way.
 


Not his best vid but I quite like this guy.
Skip to 20 mins for this particular earth problem, but ideally watch it all.

Obviously not your vehicle but maybe some of his testing tips may help.

If you've actually tested your sensors then that's good, and you can ignore this.
 
Last edited:
OK, a further update -

Plugged the LPG system back in - just to see what was what, ran better but still faltered.

Used the LPG diagnostics to monitor O2 sensor switching and they are switching rich/lean/rich as they should looking at the trace....



So, I am guessing it is not them.....and the MAF seems to check out too, engine dies if disconnected and engine won't start without coaxing it to be above 550rpm.

It sounded and felt like it had a misfire, so I pulled the injector wiring off one by one and No.6 made no difference to the way the engine sounded.....So thinking it could be plug not firing or injector issue, I put on my plug tester lamps and they are all firing (the vid looks like they are missing a few flashes, but that is due to the camera shutter speed and framerate missing a few - they do all indeed work and flash constantly as they should!)



I also tried this with the LPG system and removed No.6 LPG injector and still no change in engine note.

The LPG system plugs into the original Petrol injector connector, goes to the LPG ECU and then back out to the petrol injector again.....it uses the petrol injector pulse to fire the LPG injector via the LPG ECU, if the LPG ECU doesn't get a signal, it doesn't fire that injector.....hence why if I unplug the petrol injector when running on petrol the note doesn't change, and similarly, when running on gas, removing the LPG injector also makes no change to the engine running....

So, next up is to check the wiring from the GEMS ECU to the injector connector and also the LPG harness from petrol connection and back to petrol connection....

Such fun.
 
myfirstl322 said:
Have you checked #6 injector for a dead short?
Click to expand...
That is part of the ongoing investigative work...the fact it also does it on LPG which relies on the petrol injector signal (you unplug the petrol connector, plug this into the LPG ECU and then plug the LPG harness into the petrol injector and the LPG injector) makes me think it is wiring harness issues - as the LPG system isn't getting a 'fire No.6' signal from the petrol wiring harness.
 
No experience on this, but my thinking was that an injector would have a feedback wire in order to define modulation.

Tronics is a major deficiency for me, every car iv'e owned has behaved, leaving me time to polish my spanners.
 
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